Optical measurement of three-photon absorption coefficient in GaAs semiconductor

Multi-photon absorption can be used as a negative feedback device in laser cavity to control the intensity and width of laser pulse. Also it is a very effective nonlinear spectrum technique in the study on mutual effect between the ultrashort laser pulse and semiconductor. Using the NLT (nonlinear transmission) technique, the experimental investigation on three-photon absorption processes in GaAs intrinsic semiconductor excited by a pulsed laser at 2.06 μm is reported for the first time. Three-photon absorption and subsequent excited state absorption of the generated electrons and holes are observed. Three-photon absorption coefficient is measured and the experimental result is in good agreement with the theoretical value. The experimental setup and the measuring method are described.